Study On Phosphate Adsorption Characteristics Of Spontaneous Combustion Coal Gangue In Water

Coal gangue is one of the largest industrial solid wastes in China.Due to the low utilization rate,it is easy to spontaneous combustion under certain natural conditions to form spontaneous combustion coal gangue,and discharge toxic gas.In order to improve the utilization of spontaneous combustion coal gangue,ease its environmental pollution.In this paper,the adsorption performance and adsorption mechanism of spontaneous combustion coal gangue on phosphate in water were investigated by using spontaneous combustion coal gangue as adsorbent.The results are as follows:The main components of spontaneous combustion of coal gangue are SiO2 and Al2O3,belonging to the clay minerals,which has a certain adsorption for phosphate.Spontaneous combustion coal gangue has almost no organic matter.The crystal structure detected by XRD is only quartz.According to BET,BJH calculated spontaneous combustion coal gangue specific surface area is 4.95 m2·g-1,pore volume and pore size were 0.016 cm2·g-1,3.82 nm,respectively.The pore structure belongs to mesopores.The adsorption capacity of phosphate in the aqueous solution is better.When the total phosphorus concentration is 5 mg·L-1,the removal rate of phosphate can reach 93%.The adsorption pattern of spontaneous combustion coal gangue to phosphate is in accordance with Langmuir isothermal adsorption mode,thus the adsorption process occurs on the surface of uniform monolayer adsorbent.According to Langmuir,the theoretical maximum adsorption capacity Qm is 7.07 mg·g-1.The adsorption process of spontaneous combustion coal gangue is in accordance with the pseudo-second-order kinetics equation and the particle diffusion equation,indicating that the adsorption process includes chemical adsorption and physical adsorption.The ?H>0,?S>0,?G<0 indicate that spontaneous combustion coal gangue is spontaneous and endothermic physicochemical adsorption process.Spontaneous combustion coal gangue after high temperature combustion,the stability of the crystal structure was part of the destruction,iron and calcium and other metal oxides increased,so that coal gangue activity increased.So the main reaction mechanism is anion exchange and chemical precipitation reaction.